Field of the Invention
The present invention relates to metal shaping, and more particularly to a mill stand for forming discontinuous longitudinal deformations on sheet metal.
The term "sheet metal" as used herein refers to a metal strip and the term "longitudinal deformation" refers to forming longitudinally extending deformed portions on the sheet metal in the form of corrugations running parallel at certain intervals from the edges of a strip (i.e. closed corrugations).
The mill stand of the invention is preferably designed to manufacture metal sheet panels having corrugated portions of improved rigidity with flat portions therebetween and along the sheet periphery for convenience in mounting and welding. Such panels are commonly used for manufacturing thin-walled spatial structures, such as railway cars or building metal elements.
Known in the prior art is a shaping mill (U.S. Pat. No. 3,686,917) for impressing discontinuous longitudinal deformations upon sheet metal, which comprises a stand with rolls having circumferential discontinuous congruent forming elements.
The prior art shaping mill is designed to longitudinally deform the sheet metal which is fed into the mill stand. The length of the deformed portions (corrugations) is equal to the arcuate length of the roll forming elements. Thus, should a need arise for changing corrugation lengths, it is required to use another set of rolls with forming elements having arcuate lengths conforming to the length of newly desired corrugations. However, since the maximum length of the deformed portions on the sheet metal is limited by the circumferential length of the forming rolls, any increase in length of the deformed portions may be achieved only through an increase in the forming roll diameters. Therefore, when the corrugation lengths are to be changed, it is necessary to change forming rolls, which calls for re-setting the mill stand and, consequently, additional expenses in preparing and setting up a new set of rolls. In addition, corrugations of increased lengths call for bigger roll diameters, which in turn requires an increased metal consumption and enlarged overall dimensions of the mill stand which is impractical because of its larger size.
Known in the prior art devices which make it possible to produce sheet metal panels with corrugations having a length greater than that of the circumference of the forming rolls.
There is known a method and an apparatus for deforming sheet material (British Pat. No. 1,193,831). The apparatus is a mill stand for longitudinally deforming certain portions on sheet material. The stand comprises a frame member with forming rolls having congruent circumferential forming elements, the number of which corresponds to the number of corrugation to be formed on sheet metal, a power cylinder (pneumatic or hydraulic) connected with one of the forming rolls for a vertical reverse motion of this roll, and a system for feeding a working medium to the power cylinder. This system includes a means (slide valve) for controlling the power cylinder. The stand is also provided with a master device interacting with the means for controlling the power cylinder. The master device is composed of a plurality of proximity limit switches.
When the apparatus described above is in operation, sheet metal in the form of separate strips (blanks) of finite lengths is fed into the forming stand. In passing between the forming rolls, the leading end of the blank is not subjected to deformation but as soon as it approaches the proximity limit switch mounted downstream of the mill stand, there is produced a command for actuating the slide valve to pass the working medium (hydraulic fluid or air) into the power cylinder. A rod of the cylinder moves one of the forming rolls, thereby bringing the forming rolls together. The process of longitudinally deforming blank portions begins, i.e. a number of corrugations parallel to each other are impressed upon the sheet metal. When the corrugations are formed in the blank, the tail end of the blank acts upon another proximity limit switch mounted before the roll axis plane. This is followed by a command for actuating the slide valve to move the hydraulic cylinder upwardly. Thus, the rolls are separated, the deformation process is ceased and the corrugated article with a flat portion at its tail end leaves the clearance between the rolls.
Since the deformation process is started and ceased depending on the position of the leading and tail ends of a blank, the mill stand described above is unsuitable for deforming sheet metal fed thereto in the form of a continuous strip. Therefore, prior to being deformed, metal strip coils are cut into blanks of finite length. In addition, to deliver separate blanks into the mill stand, provisions are made for guiding the leading end of each blank into the clearance between the forming rolls. This leads to decreasing the blank supply rate and, consequently, slows the longitudinal deformation process.
In addition, since the starting and end moments of the deformation process are dependent on the position of the leading and tail ends of a blank of finite length, it is impossible to impress thereupon a plurality of discontinuous longitudinally corrugated portions.
It is, therefore, an object of the invention to provide a mill stand of improved efficiency for forming discontinuous longitudinal deformations on sheet metal.
Another object of the invention is to provide a mill stand which makes it possible to form discontinuous longitudinally extending deformations on sheet metal in the form of a continuous strip continuously fed into the stand.
Yet another object of the invention is to provide a mill stand which makes it possible to form discontinuous longitudinal deformations on sheet metal with practically any longitudinal spacing between the deformed portions.
A further object of the invention is to provide a mill stand which makes it possible to control the length of the portions which are longitudinally deformed on the sheet metal.
A still further object of the invention is to provide a mill stand which makes it possible to manufacture sheet metal articles with constant longitudinal spacings between the longitudinally deformed portions.